vitamin B12 deficiency is characterized by macro-ovalocytosis
(mean cell volume >100 fL) in a peripheral smear with hypersegmented
polymorphonuclear leukocytes (at least one neutrophil with six or
more lobes or 5% neutrophils with five lobes).
features include leukopenia and thrombocytopenia; increased lactic
dehydrogenase and bilirubin levels suggest ineffective erythropoiesis.
marrow examination may show megaloblastic changes.
B12 deficiency may potentiate mental illness and further damage neurons
and myelin sheaths.
anaemia accounts for 80% of cases of megaloblastic anaemia due to
impaired absorption of vitamin B12
may be an increase in plasma unconjugated bilirubin due to
increased destruction of red-cell precursors in the marrow.
and thyroid function tests and protein electrophoresis may help in
the differential diagnosis of macrocytosis.
can be caused by insufficient stomach acid - necessary to separate
B12 from ingested protein.
is the most common cause of B12 deficiency in the elderly and individuals
on drugs that suppress gastric acid production.
may also be due to a lack of intrinsic factor, a substance
produced by parietal cells in the stomach that binds with B12 before
absorption by the intestines.
condition called pernicious anemia involves damage to the parietal
cells, resulting in decreased production of intrinsic factor.
for pernicious anemia, although repletion of vitamin B12 should be
expected to result in a cessation of anemia-related symptoms, a halt
in neurological deterioration, and (in cases where neurological problems
not advanced) neurological recovery and a complete and permanent remission
of all symptoms, so long as B12 is supplemented.
B12 deficiency anemia is treated with supplements of vitamin B12.
the level of vitamin B12 has returned to normal, your body will produce
more red blood cells and the symptoms will go away.
most people need to take supplements for the rest of their lives
to prevent the condition from returning.
is because the usual cause of vitamin B12 deficiency is poor absorption
of the vitamin through the intestine.
stop taking the supplements, your B12 level will fall again.
of vitamin B12 deficiency or pernicious anemia consists of high
doses of vitamin B12 supplements. If you have have the deficiency
but no symptoms, the vitamin may be taken by mouth. Blood tests are
done periodically to make sure the vitamin B12 level returns to and
who have symptoms due to nerve damage are usually given vitamin B12
by injection into a muscle.
which may be self-administered, are given daily or weekly for several
weeks until the vitamin B12 level returns to normal.
injections are given once a month indefinitely, unless the
disorder causing it can be corrected. Anemia usually resolves in about
6 weeks. But severe symptoms due to nerve damage-for example, dementia
in older people-may not resolve.